add a changelog file (CHANGES.txt, or something like that)

[bart9h]

While updating my Void Linux system, I noticed that delta was updated from 0.17 to 0.18.

"Cool, let's check what's new."

Nope, there is no changelog in the source tree. And checking the git commit log is not an acceptable alternative.

Pleas just provide a simple list like:

version x.y.z
=============

- Add this new feature.
- Fixed that bug.
- ...